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Regents Biology
38.3 – Excretory System
Regents Biology
Objectives § Explain how animals manage toxic nitrogenous waste § Discuss the 3 types of nitrogenous waste § Contrast the way in which aquatic animals eliminate
waste with that of terrestrial animals § Identify the components of the human excretory system
and discuss their functions § Explain how “form fits function” by citing specific
examples from the excretory system
Regents Biology
§ Animal cells move material across the cell membrane by diffusion
§ What sort of materials?
What do animal cells do to stay alive?
Regents Biology
Unicellular to Multicellular
§ All cells in direct contact with environment à can easily get nutrients in and waste out by diffusion
§ Internal cells not in direct contact with environment à can’t easily get nutrients in and waste out
§ need organ systems
Regents Biology
What liquid waste do we make? § Digesting protein makes poison (ammonia)
Regents Biology
§ ammonia (freshwater)
§ urea (land) § uric acid (egg
layer)
Nitrogen waste
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Nitrogen waste disposal in water § lots of water around à waste can be poisonous § Freshwater fish excrete ammonia through gills and as
dilute urine § Saltwater fish excrete ammonia in concentrated urine
Regents Biology
Nitrogen waste disposal on land § Land animals need to conserve water à evolved less poisonous waste product (urea)
§ excrete urea and (little) water as urine
Regents Biology
Nitrogen waste disposal in egg § Egg-laying land animals (birds, reptiles, insects) have no
place to get rid of waste while in egg à needs waste that doesn’t dissolve in water inside egg (uric acid)
§ stays a powder, doesn’t dissolve in water § Bird poop is really… pee!
Regents Biology
Regents Biology
KIDNEY
BLADDER
URETER
§ located on either side of the spinal column near the lower back
§ ureter carries urine from each kidney to bladder
Regents Biology
Renal Cortex
Renal Medulla
URETER
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§ cortex (outer) and medulla (inner) § nephrons – filters § Nephrons are located in the renal cortex (except for their
loops of Henle which descend into the renal medulla).
Regents Biology
The Kidneys § Blood enters the kidney
through renal artery. § The kidney removes: - urea - excess water - other waste products
§ The clean, filtered blood leaves the kidney through the renal vein and returns to circulation.
Regents Biology
§ Each nephron has its own blood supply (an arteriole, a venule, a network of capillaries)
§ Each nephron releases fluids to a collecting duct, which leads to the ureter.
Regents Biology
Regents Biology
Filtration and Reabsorption § The filtration of blood
mainly takes place in the glomerulus
§ Fluid from the blood flows into Bowman’s capsule.
§ Filtered from the blood: water, urea, glucose, salts, amino acids, and some vitamins
§ Plasma proteins, cells, and platelets remain in the blood
http://www.youtube.com/watch?
feature=player_embedded&v=qfWx8msgHqM
Regents Biology
§ material removed from the blood at Bowman's capsule (~ 99% of the water and most nutrients) is reabsorbed into the blood
§ Urine drains into the collecting duct
§ Loop of Henle – where water is conserved and volume of urine is minimized
Regents Biology
Osmoregulation § Urine is stored here
until it is released from the body through a tube called the urethra.
§ The activity of the kidneys is mostly controlled by the composition of the blood (osmoregulation).
Regents Biology
Kidney Disorders
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